I believe the GTTV episodes in the Gametrailers app opens a browser window that uses Flash. At least that is the case on the Boxee Box. I still haven't gotten around to trying this on the PC Boxee software to see if that message is just informational or if there is actually a problem with Flash. Honestly, I've given up on PC Boxee since the devs already did.
Boxee Box firmware: Latest
PC to Boxee Box connection: SMB over gigabit wired Ethernet.
Boxee Box buffers on BR MKVs and ISOs.
Streaming BR MKVs and ISO rips with full menus to Dune with no issues.
Streaming BR MKVs and ISO rips to two HTPCs using XBMC with no issues
PC Storing Media: Vista Home 64 bit, dual core (2.5GHz), 4GB RAM
Storage for media: 4 external WD Elements drives. 4 Hitachi 3TB drives
Router: NetGear WNR3500L-100NAS Wireless-N Gigabit Router